diff --git a/core/install.php b/core/install.php
index d367bce..c88ffee 100644
--- a/core/install.php
+++ b/core/install.php
@@ -25,8 +25,8 @@
 // The minimum version is specified explicitly, as DRUPAL_MINIMUM_PHP is not
 // yet available. It is defined in bootstrap.inc, but it is not possible to
 // load that file yet as it would cause a fatal error on older versions of PHP.
-if (version_compare(PHP_VERSION, '7.0.0') < 0) {
-  print 'Your PHP installation is too old. Drupal requires at least PHP 7.0.0. See the <a href="https://www.drupal.org/requirements">system requirements</a> page for more information.';
+if (version_compare(PHP_VERSION, '5.5.9') < 0) {
+  print 'Your PHP installation is too old. Drupal requires at least PHP 5.5.9. See the <a href="https://www.drupal.org/requirements">system requirements</a> page for more information.';
   exit;
 }
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 1deb173..eede970 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -186,7 +186,15 @@ function system_requirements($phase) {
     ];
   }
 
-  if (version_compare($phpversion, DRUPAL_MINIMUM_PHP) < 0) {
+  // @todo Remove once update support is dropped.
+  if (drupal_valid_test_ua()) {
+    if (version_compare($phpversion, DRUPAL_MINIMUM_UPDATE_PHP) < 0) {
+      $requirements['php']['description'] = t('Your PHP installation is too old. Drupal requires at least PHP %version.', ['%version' => DRUPAL_MINIMUM_UPDATE_PHP]);
+      $requirements['php']['severity'] = REQUIREMENT_ERROR;
+      return $requirements;
+    }
+  }
+  elseif (version_compare($phpversion, DRUPAL_MINIMUM_PHP) < 0) {
     $requirements['php']['description'] = t('Your PHP installation is too old. Drupal requires at least PHP %version.', ['%version' => DRUPAL_MINIMUM_PHP]);
     $requirements['php']['severity'] = ($phase === 'update') ? REQUIREMENT_WARNING : REQUIREMENT_ERROR;
     // If PHP is old, it's not safe to continue with the requirements check.